Phosphonic acid cation-exchangers and particularly sulfonic acid cation-exchangers are well known. Recently, polymers containing methylenediphosphonate units were synthesized. See, for example, U.S. Pat. Nos. 5,256,808 and 5,281,636. These polymers are widely used in ion-exchange processes, in heterogenous catalysis, and in removal of cations from various liquids.
In further examples, Alexandratos et al., in Emerging Separation Technologies for Metals and Fuels, Lakshmanan et al., eds., The Minerals, Metals & Materials Society (1993) pages 111-117 report data on several copolymer systems that utilized vinylidene diphosphonate esters along with several other monomers. This publication also disclosed the benefit of sulfonating polymerized aromatic groups in the copolymer in providing enhanced extraction of a polyvalent metal ion such as Eu(III).
In other recent work, Sundell et al., Polymer Preprints, 33:992-993 (1992), reported a complex synthesis of 1-vinylphenylpropane-2,2-bis(phosphonic acid), and its copolymerization with styrene and divinylbenzene to form a cross-linked copolymer. Those copolymers were used with palladium as hydrogenation catalysts.
This paper reported that the resulting copolymer contained 0.48 mmol of phosphonic acid/g of polymer. The paper also relates that only 75 percent of the bisphosphonic acid groups were present on the surface of the polymer and available to bind Cu(II). This paper also disclosed the relative difficulty encountered in copolymerizing the monomers due to the lack of solubility of the bis(phosphonic acid) monomer in the emulsions used.
The above authors provided further results for their hydrogenation catalysts in Sundell et al., Chem. Mater., 5(3):372-376 (1993). In that disclosure, results for four microemulsion polymer preparations were provided that showed that up to 0.48 mmol/g phosphorous could be incorporated into the copolymer with up to 82 percent of those phosphorous atoms being on the copolymer surface and accessible to Cu(II). The use of an alcoholic diluent during a second set of polymerizations provided a polymer with up to 0.59 mmol/g phosphorous, but with a still lower accessibility of only 43 percent.